U.S. Patent Application Publication No. US 2010/0242924 discloses a lawn mower including a rear frame formed of a right and left pair of side members made of sheet metal and a mounting surface supported rearwardly of the right and left side members, for example. An air-cooled engine is mounted on the mounting surface with an output shaft thereof projecting forward of a vehicle body. A muffler is disposed in a transverse position rearwardly of the engine. Fuel tanks are provided above the right and left rear wheels, respectively, to act as a fuel system. Evaporated gas separator tanks and canisters are disposed between the fuel tanks and the engine to allow fuel gas evaporated within the fuel tanks to combust in the engine. Each of the evaporated gas separator tanks is configured to recover fuel gas having evaporated within the fuel tank and direct it to the canister, and is disposed in a gas passageway between each fuel tank and each canister. The canisters are provided under the right and left fuel tanks in association with the right and left fuel tanks, respectively, to be distributed in the right and left sides of a rear portion of an oil cooler in a cooling air passageway at positions that are spaced from each other substantially equidistantly from a lateral center line of a traveling vehicle body. In such a conventional fuel system, it is required to provide long hoses for connecting between the fuel tanks, canisters and engine, which results in a complicated hose arrangement.
Further, U.S. Pat. No. 7,849,837 B2 discloses a lawn mower provided with a fuel system for performing evaporated fuel processing. Type of lawn mower includes a fuel tank disposed on a side of an engine mounted rearwardly of a vehicle frame, and a battery unit fixed to the vehicle frame rearwardly of the engine. On the fuel tank is mounted a canister communicating with an upper inner space of the fuel tank. The canister has a purge conduit extending from the opposite side of a port communicating with the fuel tank and fixed to a purge joint at a lower end thereof. In this arrangement, the canister is provided above the fuel tank, which inevitably limits a space for accommodating the canister. As a result, restrictions may be imposed in the size as well as the maintenance and inspection of the canister.